I. Field of the Invention
The present invention relates to wireless telecommunication systems. More particularly, the present invention relates to a novel and improved method and apparatus for paging a cellular telephone or other wireless communication device using a quick paging channel and a full paging channel.
II. Description of the Related Art
The IS-95 cellular telephone standard and its derivatives such as IS-95A and ANSI J-STD-008, referred to herein collectively as IS-95, use advanced signal processing techniques to provide efficient and high quality cellular telephone service. For example, an IS-95 compliant cellular telephone system utilizes decoding, error detection, forward error correction (FER), interleaving and spread spectrum modulation in order to make more efficient use of the available RF bandwidth, and to provide more robust connections. In general, the benefits provided by IS-95 include longer talk time and fewer dropped calls when compared to other types of cellular telephone systems.
To conduct communications in an orderly manner, the IS-95 standard provides a set of highly encoded channels over which data having different functions is transmitted. These highly encoded channels include a paging channel carrying paging messages for notifying cellular telephones or other types of wireless terminals that an incoming request to communicate is pending. In accordance with the IS-95 standard, paging messages are transmitted at low to medium data rates during time slots that are preassigned to groups of cellular telephones. These paging channel time slots are typically eighty milliseconds in duration. Each eighty millisecond time slot is composed of four paging channel message frames each twenty milliseconds in duration. Table I provides the data included in a General Page Message as an example of a typical paging message generated substantially in accordance with the IS-95A standard.
In the general page message, the MSG_TYPE field corresponds to the message type and is set to xe2x80x9800010001xe2x80x99; the CONFIG_MSG_SEQ field corresponds to a configuration message sequence number that is set to CONFIG_SEQ as specified in section 7.6.2.2 of IS-95A; the ACC_MSG_SEQ field corresponds to an access parameters message sequence number that is set to ACC_CONFIG_SEQ as specified in section 7.6.2.2 of IS-95A; the CLASSxe2x80x940_DONE field indicates whether Class 0 pages (as described in IS-95A) are done; the CLASSxe2x80x941_DONE field indicates whether Class 1 pages (as described in IS-95A) are done; the first RESERVED field includes reserved bits that are set to xe2x80x9800xe2x80x99; the BROADCAST_DONE field indicates whether broadcast pages are done; the second RESERVED field includes reserved bits that are set to xe2x80x980000xe2x80x99; the ADD_LENGTH field indicates the number of octets in the page message specific fields; and the ADD_PFIELD is used for any additional page message specific fields. The base station includes one occurrence of the appropriate page class record for each mobile station which is paged in the message. Page records with the PAGE_CLASS set equal to xe2x80x9811xe2x80x99 and PAGE_SUBCLASS set equal to xe2x80x9800xe2x80x99 are used to announce broadcast messages sent on the paging channel.
In order to detect paging messages, a cellular telephone periodically monitors the paging channel during the assigned paging slot. Furthermore, the cellular telephone periodically activates RF and digital signal processing circuitry for as long as necessary to process the paging message. Since. the typical paging message is relatively long, possibly extending over several paging channel frames, and transmitted by way of a highly encoded low to medium rate channel, the associated processing during each paging slot requires a significant amount time and signal processing resources.
Quite often instances occur the cellular telephone is assigned to monitor predetermined paging channel slots where is no paging message intended for the particular mobile station. Accordingly, the mobile station has consumed battery power in the signal processing of information for the duration of the slot where either the message is not intended for the mobile station or there is no message. This unnecessary processing reduces the amount of time an IS-95 compatible cellular telephone can remain in a standby mode without depleting its battery. It would be desirable to provide a system which increased the amount of time that a telephone could remain in standby mode while, at the same time, ensuring that all pages sent to the telephone are correctly received.
Paging schemes disclosed in U.S. patent application Ser. No. 08/890,355 filed Jul. 9, 1997 entitled xe2x80x9cDual Event Slotted Pagingxe2x80x9d, and in U.S. patent application Ser. No. 08/865,650 filed May 30, 1997, now U.S. Pat. No. 6,111,865, which are incorporated by reference herein, illustrate the basic implementation of a full paging channel in combination with a quick paging channel to provide terminal paging.
The present invention is directed to a mobile radio communication system that includes a base station, a plurality of terminals, a full paging channel with paging slots for transmitting paging information to the terminals, and a quick paging channel containing terminal specific paging indicators. The indicators provided within a quick paging slot instruct specific terminals to monitor the paging channel.
The present invention also includes a method for determining paging information from a pilot signal received by way of a pilot channel. In this method, a pilot signal value is determined from the received pilot signal, and the paging information is then determined according to the pilot signal value. The system optionally includes an on-off keying signal within the quick paging channel to instruct a terminal to monitor the paging channel.
A telephone paging system in accordance with the present invention can also include information packets within the quick paging channel. The information packets are associated with terminals and function to instruct the associated terminals to monitor the paging channel. Reserved information packets are provided to instruct a plurality of terminals to perform telephone operations and to instruct a plurality of terminals not to perform telephone operations. The information packets can have a bit for indicating that a subsequent information packet has a further bit for instructing a terminal to monitor the paging channel.
The quick paging channel in an exemplary embodiment is an uncoded, on-off keying (OOK) modulated direct sequence spread spectrum signal that is used by mobile stations operating within the coverage areas of base station. The base station uses the quick paging channel to inform mobile stations operating in the slotted mode while in the idle state whether of not they should receive information on a paging channel or other designated channels. The presently disclosed method and apparatus provides enhanced robustness to paging schemes using a slotted mode paging channel and a quick paging channel.